Combine the cream cheese and powdered sugar, fold in the whipped cream, and refrigerate for 1-2 hours.
Beat the egg whites, sugar, vanilla extract, and salt until glossy. Combine the canola oil, milk, and flour, and fold this mixture into the egg white mixture. Line a 7-inch springform pan, 6-inch springform pan, and 4-inch mini springform pan with parchment paper and divide the sponge cake batter between the 3 cake pans. Transfer the 3 cake pans to a preheated oven and cook at 350°F for approximately 1 hour.
After 1 hour, remove the 7-inch springform cake pan and the 4-inch mini springform cake pans from the oven and let cool. Reduce the oven temperature to 200°F and let the cake in the 6-inch springform pan cook for another 20 minutes. Remove the 6-inch springform cake pan from the oven and press a 5-inch glass bowl into the sponge cake to create a hollow. Remove the bowl and the springform ring and coat the outside of the 6-inch sponge cake with the chilled cream cheese frosting. Remove the springform rings from the cooled 7-inch and 4-inch sponge cakes and coat the outside and tops of the cakes with the chilled cream cheese frosting. Refrigerate all 3 frosted cakes for 30 minutes.
Line the base of a 6-inch springform pan with parchment paper and arrange the red & white hard candies in alternating color circles. Transfer the springform pan base to a preheated oven and cook at 250°F for about 20 minutes, until the hard candies have melted together into a cohesive circle. Remove the springform pan base from the oven and let the hard candy plate harden at room temperature for 30 minutes.
Prepare the green candy melts according to the instructions on the packaging. Dip the cream puffs in the melted green chocolate, decorate with red & white sprinkles, and refrigerate for 10 minutes.
Place the frosted 7-inch sponge cake on a cake platter, top with the frosted 6-inch sponge cake, and place the hard candy plate on top. Place the frosted 4-inch sponge cake on top of the hard candy plate and decorate the outside of the 3-tier cake with the chilled cream puffs to make it look like a Christmas tree.
Finally, sprinkle powdered sugar over the Christmas tree cake (if you're feeling especially festive, you can mix some edible white or silver glitter into the powdered sugar for a shimmering touch). To serve, remove the top portion of the Christmas tree cake and pour the warmed cranberry sauce into the hollow of the 6-inch sponge cake – the cream puffs taste especially great dipped in the holiday sauce!